The explanation of nº 3 in the opposite in Sintra.
Sintra, for those who do not know, was land of Templars, Freemasonry, Priories and Orgies.
It seems that the fact that the number is upside down was a signal for outsiders to identify the site of the secret cult.
That door belongs to the old Hotel Victor – frequented by Eça, Camilo, Ramalho and other great intellectuals of the 19th Century.
It is also worth remembering that Victor Sasseti, the owner of the Hotel Bragança in Lisbon, a freemason and a close friend of António Carvalho Monteiro and Luigi Manini, who designed the Sasseti Cottage, on the hillside of the Moors, now Property of the City hall.
Of course Sasseti put the number upside down on purpose!
In this village (Sintra) everything has a certain secret spirit.
The inverted three, like the inverted triangle, represents the masculine principle.
The number three, such as five or seven, has important Masonic connotations (for example, the three symbols of Freemasonry are the Square, Level, and Plumb line).
Three are also the Graces, as you can see in the Regaleira panel.
Not to mention the triplicity of time (past, present and future) and other things.
Or: The inverted number 3 becomes an “E,” and is called the “power of 3”.
This letter represents the eye (of Horus).
It symbolizes Mars. It represents talent. It represents war. It also represents the Star of David.
The 3 inverted is linked to relieving stress and anxiety.
An oratorical technique for controlling the listeners used by Freemasonry is to use this power of the inverted 3 or eye, dividing the oratory into 3 topics, because the brains of the listener assimilate better than 2 or 4.
That inverted 3-plaque may even simply represent a Jewish house, a way of saying it to the world without the understanding of most people.